This study assesses the effects of a new drug, alosetron, on transit through the digestive tract and on rectal sensation in patients with irritable bowel syndrome over a 12-week period. We have completed this study and wish to close it. This study explored the mechanism of the beneficial clinical effect of alosetron in patients with irritable bowel syndrome. We are still completing data analyses and have not unblinded the investigators. Therefore, no conclusion can be reported here.